HTTP/1.1, part 7: AuthenticationDay Software23 Corporate Plaza DR, Suite 280Newport BeachCA92660USA+1-949-706-5300+1-949-706-5305fielding@gbiv.comhttp://roy.gbiv.com/One Laptop per Child21 Oak Knoll RoadCarlisleMA01741USAjg@laptop.orghttp://www.laptop.org/Hewlett-Packard CompanyHP Labs, Large Scale Systems Group1501 Page Mill Road, MS 1177Palo AltoCA94304USAJeffMogul@acm.orgMicrosoft Corporation1 Microsoft WayRedmondWA98052USAhenrikn@microsoft.comAdobe Systems, Incorporated345 Park AveSan JoseCA95110USALMM@acm.orghttp://larry.masinter.net/Microsoft Corporation1 Microsoft WayRedmondWA98052paulle@microsoft.comWorld Wide Web ConsortiumMIT Computer Science and Artificial Intelligence LaboratoryThe Stata Center, Building 3232 Vassar StreetCambridgeMA02139USAtimbl@w3.orghttp://www.w3.org/People/Berners-Lee/
The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypermedia information
systems. HTTP has been in use by the World Wide Web global information
initiative since 1990. This document is Part 7 of the seven-part specification
that defines the protocol referred to as "HTTP/1.1" and, taken together,
obsoletes RFC 2616. Part 7 defines HTTP Authentication.
This version of the HTTP specification contains only minimal editorial
changes from (abstract, introductory paragraph,
and authors' addresses). All other changes are due to partitioning the
original into seven mostly independent parts. The intent is for readers
of future drafts to able to use draft 00 as the basis for comparison
when the WG makes later changes to the specification text. This draft
will shortly be followed by draft 01 (containing the first round of changes
that have already been agreed to on the mailing list). There is no point in
reviewing this draft other than to verify that the partitioning has been
done correctly. Roy T. Fielding, Yves Lafon, and Julian Reschke
will be the editors after draft 00 is submitted.
Discussion of this draft should take place on the HTTPBIS working group
mailing list (ietf-http-wg@w3.org). The current issues list is
at
and related documents (including fancy diffs) can be found at
.
This document will define aspects of HTTP related to access control and
authentication. Right now it only includes the extracted relevant sections
of RFC 2616 with only minor edits.
HTTP provides several OPTIONAL challenge-response authentication
mechanisms which can be used by a server to challenge a client
request and by a client to provide authentication information. The
general framework for access authentication, and the specification of
"basic" and "digest" authentication, are specified in "HTTP
Authentication: Basic and Digest Access Authentication" . This
specification adopts the definitions of "challenge" and "credentials"
from that specification.
The request requires user authentication. The response MUST include a
WWW-Authenticate header field () containing a challenge
applicable to the requested resource. The client MAY repeat the
request with a suitable Authorization header field (). If
the request already included Authorization credentials, then the 401
response indicates that authorization has been refused for those
credentials. If the 401 response contains the same challenge as the
prior response, and the user agent has already attempted
authentication at least once, then the user SHOULD be presented the
entity that was given in the response, since that entity might
include relevant diagnostic information. HTTP access authentication
is explained in "HTTP Authentication: Basic and Digest Access
Authentication" .
This code is similar to 401 (Unauthorized), but indicates that the
client must first authenticate itself with the proxy. The proxy MUST
return a Proxy-Authenticate header field () containing a
challenge applicable to the proxy for the requested resource. The
client MAY repeat the request with a suitable Proxy-Authorization
header field (). HTTP access authentication is explained
in "HTTP Authentication: Basic and Digest Access Authentication"
.
This section defines the syntax and semantics of all standard
HTTP/1.1 header fields. For entity-header fields, both sender and
recipient refer to either the client or the server, depending on who
sends and who receives the entity.
A user agent that wishes to authenticate itself with a server--
usually, but not necessarily, after receiving a 401 response--does
so by including an Authorization request-header field with the
request. The Authorization field value consists of credentials
containing the authentication information of the user agent for
the realm of the resource being requested.
HTTP access authentication is described in "HTTP Authentication:
Basic and Digest Access Authentication" . If a request is
authenticated and a realm specified, the same credentials SHOULD
be valid for all other requests within this realm (assuming that
the authentication scheme itself does not require otherwise, such
as credentials that vary according to a challenge value or using
synchronized clocks).
When a shared cache (see Section 2.7 of ) receives a request
containing an Authorization field, it MUST NOT return the
corresponding response as a reply to any other request, unless one
of the following specific exceptions holds:
If the response includes the "s-maxage" cache-control
directive, the cache MAY use that response in replying to a
subsequent request. But (if the specified maximum age has
passed) a proxy cache MUST first revalidate it with the origin
server, using the request-headers from the new request to allow
the origin server to authenticate the new request. (This is the
defined behavior for s-maxage.) If the response includes "s-maxage=0",
the proxy MUST always revalidate it before re-using
it.If the response includes the "must-revalidate" cache-control
directive, the cache MAY use that response in replying to a
subsequent request. But if the response is stale, all caches
MUST first revalidate it with the origin server, using the
request-headers from the new request to allow the origin server
to authenticate the new request.If the response includes the "public" cache-control directive,
it MAY be returned in reply to any subsequent request.
The Proxy-Authenticate response-header field MUST be included as part
of a 407 (Proxy Authentication Required) response. The field value
consists of a challenge that indicates the authentication scheme and
parameters applicable to the proxy for this Request-URI.
The HTTP access authentication process is described in "HTTP
Authentication: Basic and Digest Access Authentication" . Unlike
WWW-Authenticate, the Proxy-Authenticate header field applies only to
the current connection and SHOULD NOT be passed on to downstream
clients. However, an intermediate proxy might need to obtain its own
credentials by requesting them from the downstream client, which in
some circumstances will appear as if the proxy is forwarding the
Proxy-Authenticate header field.
The Proxy-Authorization request-header field allows the client to
identify itself (or its user) to a proxy which requires
authentication. The Proxy-Authorization field value consists of
credentials containing the authentication information of the user
agent for the proxy and/or realm of the resource being requested.
The HTTP access authentication process is described in "HTTP
Authentication: Basic and Digest Access Authentication" . Unlike
Authorization, the Proxy-Authorization header field applies only to
the next outbound proxy that demanded authentication using the Proxy-Authenticate
field. When multiple proxies are used in a chain, the
Proxy-Authorization header field is consumed by the first outbound
proxy that was expecting to receive credentials. A proxy MAY relay
the credentials from the client request to the next proxy if that is
the mechanism by which the proxies cooperatively authenticate a given
request.
The WWW-Authenticate response-header field MUST be included in 401
(Unauthorized) response messages. The field value consists of at
least one challenge that indicates the authentication scheme(s) and
parameters applicable to the Request-URI.
The HTTP access authentication process is described in "HTTP
Authentication: Basic and Digest Access Authentication" . User
agents are advised to take special care in parsing the WWW-Authenticate
field value as it might contain more than one challenge,
or if more than one WWW-Authenticate header field is provided, the
contents of a challenge itself can contain a comma-separated list of
authentication parameters.
TBD.
This section is meant to inform application developers, information
providers, and users of the security limitations in HTTP/1.1 as
described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make
some suggestions for reducing security risks.
Existing HTTP clients and user agents typically retain authentication
information indefinitely. HTTP/1.1. does not provide a method for a
server to direct clients to discard these cached credentials. This is
a significant defect that requires further extensions to HTTP.
Circumstances under which credential caching can interfere with the
application's security model include but are not limited to:
Clients which have been idle for an extended period following
which the server might wish to cause the client to reprompt the
user for credentials.Applications which include a session termination indication
(such as a `logout' or `commit' button on a page) after which
the server side of the application `knows' that there is no
further reason for the client to retain the credentials.
This is currently under separate study. There are a number of work-arounds
to parts of this problem, and we encourage the use of
password protection in screen savers, idle time-outs, and other
methods which mitigate the security problems inherent in this
problem. In particular, user agents which cache credentials are
encouraged to provide a readily accessible mechanism for discarding
cached credentials under user control.
Based on an XML translation of RFC 2616 by Julian Reschke.
HTTP/1.1, part 6: CachingDay Softwarefielding@gbiv.comOne Laptop per Childjg@laptop.orgHewlett-Packard CompanyJeffMogul@acm.orgMicrosoft Corporationhenrikn@microsoft.comAdobe Systems, IncorporatedLMM@acm.orgMicrosoft Corporationpaulle@microsoft.comWorld Wide Web Consortiumtimbl@w3.orgHypertext Transfer Protocol -- HTTP/1.1University of California, Irvinefielding@ics.uci.eduW3Cjg@w3.orgCompaq Computer Corporationmogul@wrl.dec.comMIT Laboratory for Computer Sciencefrystyk@w3.orgXerox Corporationmasinter@parc.xerox.comMicrosoft Corporationpaulle@microsoft.comW3Ctimbl@w3.orgHTTP Authentication: Basic and Digest Access AuthenticationNorthwestern University, Department of Mathematicsjohn@math.nwu.eduVerisign Inc.pbaker@verisign.comAbiSource, Inc.jeff@AbiSource.comAgranat Systems, Inc.lawrence@agranat.comMicrosoft Corporationpaulle@microsoft.comNetscape Communications CorporationOpen Market, Inc.stewart@OpenMarket.com